There is a need for a totally implantable pressure transducer which can be read repeatedly without violating body tissues for extended periods of time. This device has potential value in the treatment of multiple systems trauma. We have done preliminary research on a device which would require a simple x-ray to read. The pressure sensor is a floppy bag inserted in a body cavity or into soft tissues. The bag is filled with a non-radiopaque liquid and is connected by a tube to the interrogator where it enters s coiled capillary with standardized markings. Within the capillary tube there is a fluid-fluid interface where the radiopaque solution is in contact with a non-miscible aqueous solution. The column of radiopaque solution continues through the capillary system until it ends in a gold plated nickel-bellow (about the size of a penny) which sits below the skin surface. The diameter of the tubes, the calibration ofthe bellows and the components of the floppy bag are such that one can directly read barometric compensated pressures by x -raying the capillary tube and observing the displacement of the radiopaque marker. The device uses biologically safe materials and could be stable for many years. Phase I of this study will consist of engineering and materials analysis and should be completed within 8 months. Phase II will consist of extensive long term laboratory testing and will consist of a series of implants in animals. Preliminary bench testing of the principals involved indicate that this is a workable approach to the problem of long-term pressure measurement in multiple trauma patients. It also may have significant applicability in laboratory research studying physiologic and pathologicphenomena.